Spatial distribution and air-soil exchange of short and medium chain chlorinated paraffins in Lahore, Pakistan

This study provides the first systematic data on the distribution of short- (SCCPs) and medium chlorinated paraffins (MCCPs) in the atmosphere and surface soils of Lahore, Pakistan. The spatial distribution of SCCPs and MCCPs in air (n = 12) and soil (n = 15) was investigated from industrial, residential, commercial, conventional e-waste burning and background areas of Lahore. The concentrations ranged from below the limit of detection (<LOD)-130 and <LOD-74 ng/g dw for SCCPs and MCCPs, respectively in soil while in air their corresponding concentrations were <LOD-2.9 and <LOD-1.1 ng/m³. Higher CPs contaminated soil and air were observed in industrial and commercial areas likely due to the use of CPs as flame retardants/plasticizers in products and metalworking. Total organic carbon (TOC), SCCPs and MCCPs in soil were not correlated with each other however, a significant association between SCCPs and MCCPs was observed in air samples. Among all the samples of soil and air C_10, Cl_7-8 and C_14,16Cl_7-8 were the predominant congeners for SCCPs and MCCPs, respectively. The comprehensive investigation of soil-air exchange for SCCPs and MCCPs revealed approximately 67 % of fugacity fractions (ffs) above 0.7, indicating net volatilization for most of the congeners. This study also revealed a notably high emission flux for SCCPs and MCCPs compared to their deposition flux, indicating that soil acted as a major source of CPs. Additionally, the emission flux for SCCPs was higher than for MCCPs, owing to their greater volatility and transport potential. A preliminary risk assessment suggested limited risks (Risk quotient <0.02) to the soil community while, the adult and toddler community had daily intakes of 5.7 and 7.2 ng/kg/day of CPs, respectively via different pathways highlighting the hotspots with high risk areas.